When TRUE: - proxy clients are placed on one Point-to-Multipoint Multicast Forward VCC and all other clients are placed on another Point-to-Multipoint Multicast Forward VCC, - all 'unknown' unicast frames and all unicast frames for LAN Destinations registered by proxy clients are forwarded on the Proxy Multicast Forward VCC ('unknown' unicast frames are not forwarded to non-proxy clients), - all unicast frames for LAN Destinations registered by non-proxy clients are forwarded on the Multicast Send VCC to that client, and - multicast and broadcast frames are transmitted on both Multicast Forward VCCs. When FALSE: - all clients are placed on a single Point-to-Multipoint Multicast Forward VCC, and - the BUS functions as a simple forwarding device (efficient, but 'dumb') with respect to unicast frames. One advantage of enabling this option is a reduction in client pertubation due to 'nuisance' unicast frames (i.e., unicast frames not destined for the client); proxy clients do not receive unicast frames destined for non-proxy clients, and non-proxy clients never receive nuisance unicast frames. Another advantage is the reduction in network bandwidth devoted to nuisance frames. The potential disadvantage is that the increased processing requirements result in a degradation of overall system performance.